1. Field of the Invention
The present invention relates to a burn-in board having a plate member mainly and a flexure prevention structure for preventing the plate member from flexing.
2. Description of Related Art
To devices such as IC packages or the like, a burn-in test is carried out in order to remove faulty devices. In the burn-in test, a burn-in board for loading a large number of devices to be tested thereon is used.
A burn-in board heretofore in use is shown in FIGS. 4A and 4B. The burn-in board shown in FIGS. 4A and 4B is one used for testing IC packages.
FIG. 4A is a perspective view showing the rear surface of a burn-in board 21 mainly. FIG. 4B is a vertical sectional view showing a state of a burn-in board 21 having a protective cover 26 attached to the rear surface thereof.
The burn-in board 21 comprises a flat plate 21a mainly on the front surface of which a large number of IC sockets 24, 24, . . . for putting on an IC packages (not shown) are arranged. On the front surface of the flat plate 21a, a circuit pattern through which a voltage is applied to the IC packages put on the IC sockets and an output signal is taken out of the IC packages corresponding to the applied voltage, is formed. An IC package is put on each of IC sockets 24, 24, by using an IC installation and removal device. The burn-in board 21 with the installed IC packages is disposed in a chamber for test.
The work for putting an IC package on each IC socket 24 by using the IC installation and removal device gives a large mechanical pressure to the IC package. Such a mechanical pressure or a vibration is transmitted to the flat plate 21a through the IC socket 24. Therefore, a flexure prevention structure is provided in the rear side of the flat plate 21a in order to prevent the board 21 from flexuring by such a mechanical pressure or the like. Concretely, a large number of square pillar-shaped supporting rods 22, 22, . . . are attached to the rear surface of the flat plate 21a to support it, as shown in FIG. 4. Because the supporting rods 22, 22, . . . would get out of position when a pressure or the like is applied to it, if the supporting rods 22, 22, were only set on the rear surface of the board 21, the supporting rods 22, 22, . . . are fixed to the rear surface of the burn-in board 21 by screwing each supporting rod or by using an adhesive.
However, the method for fixing the supporting rods 22, 22, . . . by screwing each supporting rod requires formation of screw holes for fitting male screws in the flat plate 21a, therein. Generally, almost the male screws for fitting in the screw holes are made of metal. Therefore, it is necessary for the circuit pattern formed on the front surface of the flat plate 21a to be designed to avoid the screw holes or to avoid male screws when male screws made of metal are used. As the result, design for patterning is restricted.
According to the method using an adhesive, it is difficult to select an appropriate adhesive because the burn-in test is often conducted under a strict temperature condition, that is, under a very high temperature or a very low temperature. There is also another problem that once the supporting rods are mounted to the board by using an adhesive it is hard to demount them.
Any one of the methods requires much time for a work for mounting or demounting a large number of used supporting rods 22 one by one, and therefore it is not possible to simplify the maintenance of the board.